XVII.] THE PROBLEM OF THE ORIGIN OF SPECIES. 207 



is, that organisms are in any degree susceptible of variation, 

 that variation may become indefinite in amount, if inde- 

 finite time is granted for the variations to take place, and 

 to be added together. 



I cannot admit that there is any intrinsic improbability No in- 

 in the derivation of the highest organisms by descent from impvoba- 

 the lowest : I think the improbability is all the other way. ^i^i^y. 

 It would be contrary to all the analogy of nature to sup- 

 pose that any of the highest works were ever produced at 

 once and by a single creative act ; but it is in accordance 

 with all that we know of the ways of nature to suppose 

 that species, like individuals, have been developed out of 

 simple germs. When we know that every individual Analogy of 

 organism, vegetable and animal, has been developed out individual 



>^ ° 1 1 1 • i . develop- 



of a simple structureless germ, and that there is no test, ment. 

 chemical or microscopic, by which the germ of one organism 

 can be distinguished from that of another, no matter how 

 unlike may be their mature forms ; and when we know 

 that every organic species must have had an origin, is it 

 not most natural to believe that the origin of the species 

 has been parallel to that of the individual ? The reason 

 why the theory of the origin of species by development is 

 so often regarded as improbable, and as having at least a 

 strono- presumption against it, is chiefly, I believe, that it Subject 



p -t' T • not yet 



has not yet had tnne to become familiar, it was impos- familiar, 

 sible that the development theory could be entertained at 

 all until the very great antiquity of the earth was known ; 

 for, so long as it was believed that the order of nature 

 was only coeval with human history, it was a necessary 

 inference that the organic creation came into existence all 

 at once, at the beginning of things. And it was impossible 

 that the development theory could be argued ou a right 

 basis until it w^as proved that every individual is developed 

 from a perfectly simple and unorganized germ, and until 

 the old notion that the germ was a folded-up miniature of 

 the perfect form was disproved- 



A really scientific objection to the development theory is Separation 

 the general fact that the union of distinct species will not ^^^^^^^^11 

 produce offspring, or at least not fertile offspring ; and it sterility, 



